1. Field of the Invention
The invention relates in general to a method and apparatus of growing a thin film, and more particularly to a method and apparatus of growing a liquid-deposited thin film.
2. Description of the Related Art
The method of growing a thin film can be divided into two main classes: vapor phase deposition and liquid phase deposition. The vapor phase deposition method has been widely applied to a semiconductor process and photoelectric industry. However, owing that the vapor phase deposition method requires a series of vacuum procedures in an industrial manufacturing process, it costs very much in hardware investment and manufacturing, which affects its competitive advantage in applications. Therefore, it is necessary to develop low-cost thin film deposition technology. The liquid phase deposition thin film growing technology and equipment are taking an essential role due to the features of low manufacturing cost, a larger area of film deposition and less limitation to appearance of deposition carriers.
The conventional liquid phase deposition technology is low-temperature deposition technology, which is operated in a normal pressure and low temperature 30° C.˜90° C. without applying an external electric field. The substrate is dipped in a reaction liquid and combination and deposition speed of the reactants can be controlled by adjusting reaction parameters of the reaction liquid to control to deposit a thin film on the surface of the substrate.
Referring to FIG. 1, a schematic diagram of a conventional thin-film growing apparatus is shown. A conventional thin-film growing apparatus 10 carries a constant-temperature sink 11 for controlling temperature of the reaction liquid through a heating stirrer 13. The constant-temperature sink 11 has a reaction-liquid trough 15 and a stirring device 14 is placed in the reaction-liquid trough 15. The stirring device 14 can be moved by the heating stirrer to stirring the reaction liquid in the trough 15 evenly. A pH-value detector 16 is disposed in the reaction-liquid trough 15 for controlling pH-value response of the reaction liquid. A substrate support base 12 is connected to the constant-temperature sink 11 and is inserted in the reaction-liquid trough 15 for supporting a substrate 17 to function in the reaction-liquid trough 15.
The liquid phase deposition thin film technology has two mechanisms on substrate surface deposition: (1) ion-by-ion mechanism in which ions of the reaction liquid grow the thin film directly on the surface of the substrate; (2) cluster-by-cluster mechanism in which ions of the reaction liquid are evenly compounded by cluster and then absorbed onto the surface of the substrate to grow the thin film.
The thin film grown by ion-by-ion mechanism has advantages of being thick, uniform, even and having high adhesion ability. However, another thin film grown through cluster-by-cluster mechanism in the liquid phase deposition thin film technology has uneven thickness and lower adhesion ability. Therefore, when a number of substrates are grown at the same time in the liquid phase deposition technology, the range between the substrates will affect the quality of thin-film quality. Owing that the range of the substrates is related to the composition, the concentration, the temperature, the pH-value of the reaction liquid and the character of the substrate surface, if the equipment for carrying the substrates can only carry the substrates by a constant range, variety and quality of the thin films grown on the substrates will be limited and thus applicability of the thin-film growing method will be reduced.
The thin films grown on the substrate in the conventional liquid phase deposition technology includes a thin film of ion-by-ion mechanism and a thin film of cluster-by-cluster mechanism, which worsens the quality of the thin film grown on the substrate.
Besides, when thin films are deposited on a number of substrates, the range between the substrates has to be adjusted according to composition of the reaction liquid. The issues of substrate-range adjustment and poor quality of thin film deposition both increase difficulty of process quality management, relatively reduce product throughout, and increase production cost.